Average Fruit Set Research Articles

Impact of growing conditions on vegetation, development and reproductive success of <i>Orchis purpurea</i> Huds. in the South-Eastern Crimea

The individual and population parameters of lady orchis — Orchis purpurea Huds. (Orchidaceae) under different growing conditions are compared. The onthogenetic type of cenopopulations, age, efficiency, recovery indices, vitality of individuals, plasticity index are determined. The largest number of plants is noted in forest communities. Demographical and morphological parameters differ nonsignificantly. Slight fluctuations in the vitality of individuals are noted depending on the habitat and the conditions of the growing season. The pollination success of plants in steppe biotopes is much higher than that in forest biotopes: the average fruit set in steppe biotopes was 39.63 %, in forest biotopes — 4.97—5.84 %. However, it did not affect reproductive success, the main indicator of which is the presence of new generations of plants: in all studied cenopopulations, a high proportion of individuals of the pregenerative period was noted. It is established that O. purpurea has a wide ecological amplitude and high adaptability to various conditions. It can grow in different habitats without changing morphological, demographic and ontogenetic parameters.

UGV‐Based Precision Spraying System for Chemical Apple Blossom Thinning on Trellis Trained Canopies

ABSTRACTBlossom thinning is one of the key steps in apple crop load management that improves the quality of apples, reduces stress on the trees, and avoids the likelihood of biennial bearing. Conventional chemical blossom thinning such as air‐blast spraying can lead to excessive use of chemical thinner to ensure full coverage, which can also cause leaf damage fruit russeting. In addition, a well‐trained operator is required to use these chemical spraying systems. To address these challenges, a UGV‐based precision spraying system was developed for automated and targeted chemical blossom thinning for apples. The system is capable of automatically driving along the tree row in the orchard environment during blooming stage, locating apple flower clusters to be thinned using a real‐time machine vision system, and precisely spraying the chemical thinner to the targeted flower clusters. A set of field tests were conducted to evaluate the performance of the UGV‐based target spraying system by comparing it to a conventional air‐blast sprayer (ABS) and a previous prototype named the cartesian target sprayer (CTS). Tests showed that the flower cluster detection reached a precision of 93.8%. The UGV‐based spraying system used 2.2 L of chemical thinner to finish the chemical thinning for 30 apple trees, followed by the ABS and CTS with 4.2 and 2.4 L usage, respectively. The robotic system also obtained an average fruit set of 2.2 per cluster after thinning, which was comparable to that with the air blast sprayer. The findings indicated that the robotic thinning system demonstrated a 66.7% reduction in chemical usage compared to the ABS and exhibited a 43.0% faster operational pace than the CTS, while attaining a comparable fruit set per cluster. The outcomes of the study provided guidance for developing a full scale robotic chemical thinning system for modern apple orchards.

A novel pollination robot for kiwifruit flower based on preferential flowers selection and precisely target

Manual pollination of kiwifruit flowers is a labor-intensive work that is highly desired to be replaced by mechanical/robotic operations. In this application note, a pollination robot was developed for achieving precision pollination of kiwifruit flowers in orchard. The pollination robot consists of five systems include vision system, air–liquid spray system, mechanical arm, crawler-type chassis, and control system, which could select suitable flowers and then target to their pistil for precision pollination. Field experiments were conducted in a commercial kiwifruit orchard to evaluate its feasibility and performance, which achieved an average pollination success rate of 99.3% with an average fruit set rate of 88.5%. Furthermore, compared to artificial assisted pollination methods, it could improve utilization rate of kiwifruit pollen with an average consumption of 0.15 g in 60 flowers. The validations demonstrated that this pollination robot could achieve efficient pollination for kiwifruit flowers and save pollen.

Elevated Atmospheric Ethylene and High Temperature Independently Inhibit Fruit Set But Not Vegetative Growth in Tomato

Ethylene is an essential plant hormone at low concentrations. Concentrations in the field rarely exceed 5 nmol⋅mol−1 (0.005 ppm), but it can accumulate as a gas in closed, indoor environments. These elevated levels can reduce growth and yield. Temperature alters ethylene synthesis and has the potential to influence ethylene sensitivity of crop plants in sealed greenhouses and indoor environments. We studied ethylene sensitivity of tomatoes (Solanum lycopersicum L. cv. MicroTina) using a unique, 12-chamber system. Ethylene levels of 0, 20, and 40 nmol⋅mol−1 (parts per billion) were maintained throughout the life cycle, at an air temperature of 22 or 28 °C. Yield of red fruit was three times higher at 22 than at 28 °C. There was a steady decrease in yield with increasing ethylene concentration, but vegetative growth was reduced less than 10% in any treatment. The highest ethylene concentration reduced yield to 11% of the control at 22 °C and to 4% of the control at 28 °C; the intermediate ethylene level reduced yield to 51% of the control at 22 °C and 37% at 28 °C. Regardless of temperature, filtering of ethylene in indoor environments to below 20 nmol⋅mol−1 is necessary to achieve normal fruit set and yield in tomato.

Improving fruit set and yield of tissue cultured date palm cv. Berhi by using a combined pollination technique

Tissue-cultured (TC) date palms produce no fruit or low yield due to abnormal fruit setting. To improve the yield of TC ‘Berhi’ palms, trees were pollinated using five pollen sources (Gantar, Ghannami, Mazafati, Zahedi, and Jarvis). The experiment was carried out in three replications for two successive years in a randomized complete blocks design. The fruit set, the fruit and seed physical traits at the Khalal stage, bunch weight at the Tamar and Khalal stages, ripeness of Tamar bunch, and the fruit quality at both Khalal and Tamar stages were measured and monitored. Year factor significantly affected the fruit set and the fruit and seed characteristics. Pollen sources affected fruit set and some seed characteristics significantly. Zahedi+Jarvis pollen treatment that induced 50% normal fruit set and the highest ratio of pulp to seed was found superior. It was also a top treatment in Khalal’s bunch weight (3.11 Kg). Zahedi+Gantar treatment was realized superior in Tamar’s bunch weight (6.00 Kg). Ghannami, Jarvis+Ghannami, and Zahedi+Jarvis treatments produced Khalal’s fruits with higher quality indices but Zahedi+Jarvis treatment was superior in fruit quality at the Tamar stage. Overall, the combined application of Zahedi and Jarvis pollens yielded the most desired outcomes.

An Advanced Robotic System for Precision Chemical Thinning of Apple Blossoms

Highlights A cartesian robotic spraying system was developed for precision apple blossom thinning. Flower clusters were detected and localized with deep learning model for target spraying. A communication algorithm was developed for positioning the spray end-effector to the target flowers. The cartesian robotic system greatly reduced chemical usage while maintaining thinning effectiveness in the final green fruit set. Abstract. Crop thinning, including blossom thinning, is one of the critical management strategies that determines the annual profitability of apple orchards. Challenges still remain for applying appropriate amounts of chemical thinner; if thinning is inadequate and too many fruits remain on the tree, fruit size will be small, fruit quality will be poor, and flower bud initiation for the following year’s crop may be either reduced or eliminated. Over-thinning also carries economic perils since yield and crop value in the year of application will be reduced. In addition, chemical thinning with excessive spray volume may cause leaf damage and fruit russeting. Thus, a robotic apple blossom thinning system was proposed, aiming to reduce the usage of chemical thinner while maintaining good thinning performance. The robotic system consisted of three major components: (1) a machine vision system that can identify and localize the apple flower clusters in tree canopies, (2) a cartesian robotic system with the guidance of a machine vision system to reach target flower clusters, and (3) a flat-shaped spraying nozzle connected with a solenoid valve as a spraying end-effector to deposit chemical thinner to the targeted flower clusters. A set of field tests was conducted to evaluate the performance of the robotic thinning system by comparing it to conventional air-blast and boom-type sprayers. In the test, the flower cluster detection reached a precision of 93.82%. The integrated robotic system used 2.3 L of chemical thinner to finish the chemical thinning for 18 apple trees, followed by the boom sprayer and air blast sprayer with 4.2 and 6.8 L usage, respectively. The robotic system also obtained an average fruit set of 2.4 per cluster after thinning, which was comparable to that of the air blast sprayer. The results showed that the robotic thinning system saved 66.7% and 45.5% of chemicals compared to the air-blast sprayer and boom-typed sprayers, respectively, while achieving a similar fruit set per cluster. The outcomes of the study provided guidance for developing a full-scale robotic chemical thinning system for modern apple orchards. Keywords: Apple orchard, Blossom thinning, Cartesian robot, Chemical thinning, Machine vision.

Insect Pollinator’s Role in Fruit Setting of Prosopis cineraria (L.) Druce

Insect Pollinator’s Role in Fruit Setting of Prosopis cineraria (L.) Druce

Pollination strategy of Gennaria diphylla (Orchidaceae) on the Canary Islands and on Madeira

Gennaria diphylla (Link) Parl. is a terrestrial, inconspicuous green orchid. Its distribution includes the central and western Mediterranean region as well as the Canary Islands and Madeira. Investigations on its pollination biology are scarce. In literature there are mentions of autogamy and of allogamy. Pollination and pollen import and export were studied on Tenerife and Madeira. The investigations showed autogamy plays a less important role than thought, although a caging experiment showed that the species is well capable of self-pollination. The orchid is pollinated by a variety of small moths, especially of the families Geometridae, Pyralidae and Crambidae. It is flowering in a period when few other plants flower, so there is little competition for pollinators. Complemented by autogamy this seems to be a successful strategy, as the species shows a relatively high average fruit set of 73 %.

Relationships between wild bee abundance and fruit set of Camellia oleifera Abel

AbstractCamellia oleifera Abel. is an economically important plant for edible oils. To investigate the importance of wild bee abundance at different canopy and spatial scale for fruit set of Camellia oleifera, we evaluated the relationship of bee abundance with fruit set using yellow pan trap, with additional focus on distance and wild bee abundance counts at a farm in China for 2 years. We found that yellow traps collected 95% more individual bees than the second‐best (pink) trap colour. Looking across canopy positions, the number of wild bees (including Colletes gigas, Andrena camellia, Andrena striata, Andrena hunanensis and Andrena chekiangensis) varied significantly in each year. The fruit set also varied significantly based on canopy position. In 2018, there was with an average fruit set of 34.13% in the lower canopy, 54.30% in the middle canopy and 47.41% in the upper canopy. In 2019, fruit set was 29.67% in the lower canopy, 54.15% in the middle canopy and 47.36% in the upper canopy. Comparing inter‐annual changes, only the fruit set and number of bees in the low canopy showed significant differences between 2018 and 2019. Fruit set and wild bee abundance were positively correlated in all canopy layers in each year, and there was an interactive effect between canopy and bee abundance on fruit set. Across 205 trees, growth indicators, crown size and tree height, increased significantly from 2018 to 2019, but the fruit set did not increase with the significant increase in the number of flowers. From the spatial perspective, wild bee abundance and fruit set were positively correlated, but fruit set was negatively correlated with distance from a large bee nesting aggregation nearby. Among the variables investigated, bee abundance seems to have the strongest influence on fruit set in C. oleifera.

Studies on Phenology and Reproductive Biology of Khejri [Prosopis cineraria (L.) Druce

Background: Khejri [Prosopis cineraria (L.) Druce] belongs to the family Leguminosae and subfamily Mimosoideae. The rural communities encourage the growth of Khejri in their agricultural fields as it improves grain yield and storage biomass production. It is the true multipurpose species and also called as ‘Golden Tree of Desert’, ‘Kalpvriksha’ of the desert, ‘King of desert’, ‘Love Tree’, and ‘Pride of the Desert’. For any tree improvement programme, knowledge of phenology and breeding system is pre-requisite, which also helps in understanding the evolutionary dynamics of a species. The range of genetic variability is controlled by reproductive system, which in turn controls the adaptive change. Pollination mechanisms affect seed set, fertility, gene flow, breeding systems, hybridization and genetic constitutions of tree populations. Methods: In this investigation during 2014-15, ten trees of [Prosopis cineraria (L.) Druce] growing at the research area of Forestry Department of CCS Haryana Agricultural University, Hisar were randomly selected and phenological observations were made on the selected trees at different phenophases. Through selfing, breeding behaviour was examined, by covering the inflorescence with muslin cloth bags before opening. Approximately, an equal number of buds were kept open in close vicinity of the covered branch. Reproductive capacity was estimated from the percentage of fruit setting in marked inflorescence. Result: In present study of Prosopis cineraria, the average fruit set under self-pollination was nil whereas it was 2.03 per cent in open natural pollination. This study confirms previous studies that Prosopis cineraria is a cross-pollinated species.

Đặc tính ra hoa và phát triển trái sầu riêng Bí Rợ (Durio zibethinus Murr.) hạt lép tại huyện Phụng Hiệp, tỉnh Hậu Giang

This study was conducted to determine the biological charateristics of flowering and fruit development of ‘Bi Ro hat lep’ durian in Tan Binh commune, Phung Hiep district, Hau Giang province from August 2018 to July 2019. An experiment was implemented using seven ‘Bi Ro hat lep’ durian trees at the age of 8-year-old, grafted on ‘Kho qua xanh’ root stocks. Results showed that anthesis occurred within 12 days with a peak appearing in day 5, primarily at 16:00 to 17:00. The average fruit set rate was 87%. Fruit development process took place within 96 days after fruit set (DAFS). Young fruit abscission occurred mostly from 0-14 DAFS (42,2%). Durian fruit developed over three stages, i.e. slow (0-28 DAFS), fast growing (28-70 DAFS) and the mature-ripen stage (70-96 DAFS). Fruit flesh started to grow from 42 DAFS. Fruit reached to the maximum growing rate on 56 DAFS. At harvesting time, average fruit weight was 2,298.0±503.1 g, with an edible portion of 27%. The percentage of seedless fruit was 63%. Wet core, a kind of physical disorder, appeared at 70-96 DAFS. The phenomenon was observed on 14,8% of locule/fruit and 13,1% of aril.

Characterization of the reproductive performance of a collection of grapevine cultivars

Genetic, physiological and environmental factors interact to determine the number of flowers in the inflorescence and the fruitset rate of grapevine. Abnormal behavior in reproductive performance may cause coulure or millerandage, which may affect yield. In this work, the reproductive performance of a set of 120 wine-grape and table-grape cultivars was studied in two consecutive growing seasons (2016 and 2017). Reproductive performance was measured in ten inflorescences from different plants in each cultivar. It included flower number per inflorescence, berry number per bunch, fruitset rate, coulure index, and millerandage index. The number of flowers per inflorescence was estimated from the number of flower caps collected in fine mesh bags set just before bloom. After flowering, flower caps from each individual bag were scanned and the digital images were used for manual or automatic counting, using a specially dedicated tool developed with ImageJ software. The same clusters used for flower counting, conveniently tagged, were cropped at harvest time, and several bunch components were measured. The average fruitset rate among all the cultivars was about 44%. The range of variation among cultivars was very high for fruitset, more than 90% every year. Differences in fruitset between seasons were also very variable among cultivars, with an average difference of around 9-10% and a range of 0-40%. Regarding coulure and millerandage, there was also great variability among cultivars, while, between seasons, they were stable: on average, about 1 point of difference on a scale of 0-10. The results obtained for these reproductive performance variables allowed us to establish a preliminary clustering of the cultivars in three separate classes. The high variability found for these key parameters between grapevine cultivars provides a very suitable base to study the genetic processes involved in grapevine reproductive performance.

Fruit set, yield and carpological characteristics of five almond cultivars (Prunus dulcis (Mill.) D.A. Webb) as affected by different soil management in southern Italy

Almond cultivation is of considerable importance among fruit crops of the warm-temperate climate and has been growing steadily worldwide since the early 1990s, reaching about 1.87 million cultivated hectares in 2016. In the Mediterranean Region, where the main parts of almond orchard are located, high erosion rates have been observed in many tree crops, including almond. Tillage is the traditional and prevailing soil management technique in the Mediterranean Basin despite many studies reported negative effects on soil quality highlighting the significant increase of soil erosion determined by this technique. But very few data are available in the literature, especially for almond, about the effects on vegetative and reproductive activities, yields and fruit quality of tree crops. The trial aimed to evaluate the effect of three different soil management techniques (‘conventional tillage’, ‘no-till without cover crop’, ‘frequently mown cover crop’) on five almond cultivars (‘Ferragnes’, ‘Filippo Ceo’, ‘Genco’, ‘Supernova’, ‘Tuono’), grown in a commercial almond orchard located in Southern Italy. Average fruit set, yield tree(-1) and dimensional parameters of fruits and kernel were determined. The tested cultivar showed difference in their fruiting behaviour regarding the distribution of both floral buds and fruits on different types of bearing shoots. This suggested, with the aim to increase productivity, that during pruning it is necessary to mainly preserve a different type of shoots in each one of these cultivars. For all the cultivars evaluated, quite negative effects resulted in terms of both yield and carpological parameters for the ‘no tillage’ treatment, while the best performances were observed for the ‘conventional tillage’ treatment.

Seasonal Fluctuations in Pollen Production and Viability in Eggplant and the Quality of Seed-Containing and Seedless (Auxin-Set) Fruits

This study investigates the influence of climate on pollen production and viability of two eggplant cultivars cultivated throughout the year in a greenhouse within the Mediterranean basin and the efficacy of auxin application to produce marketable fruit under unfavourable climatic conditions. The pollen yield per flower of both cultivars was highest during November and lowest in January and July, when air temperatures were lowest and highest, respectively. Pollen germination and tube growth in vitro were highest in spring and autumn irrespective of the cultivar. Under low night temperatures (< 15 °C), normal fruit set was not possible due to inadequate pollen production and viability, whereas the application of β-naphthoxyacetic acid to emasculated flowers enabled parthenocarpic/seedless fruit development. When pollen was not a limiting factor, both seed-containing and parthenocarpic fruit were produced. Initially, parthenocarpic fruit developed more rapidly than fruit set by pollination. However, by market maturity, both fruit types of either cultivar were similar in mean weight, size, and shape. Moreover, the external colour of seedless and seed-containing fruit was similar, whereas the percent dry matter of the seedless fruit tended to be lower. We conclude that because at times of excessively low or high temperatures pollen production and viability are adversely affected, fruit set requires assistance. In eggplant, application of the fruit-setting compound β-naphthoxyacetic acid results in the setting of seedless fruit that are similar in size and appearance to those set by natural pollination.

The Effect of Phytoplasma Disease Caused by ‘Candidatus Phytoplasma prunorum’ on the Phenological and Pomological Traits in Apricot Trees

‘Candidatus Phytoplasma prunorum’, the causal agent of European stone fruit yellows (ESFY), is one of the most important pathogens causing considerable economic losses in stone fruit orchards. This study evaluated trees infected and noninfected by phytoplasma ESFY of 16 apricot varieties grown in an orchard in Lednice (Czech Republic) between the years 2008-2014. Pomological traits, phenophases, pollen germination and seed viability were analysed as well as the presence of ‘Ca. P. prunorum’ in pollen, flower organs, fruit flesh, immature seeds and seedlings by nested PCR. One of the most detrimental impacts was the decreased fruit set of infected trees which occurred in 12 out of 16 studied varieties reaching an average fruit set decrease of 16.1%. Pollen germination rates also suffered, showing an average decrease by 11.78% in infected trees. In the analysis of some traits, overall significant differences were observed between the infected and noninfected trees. However, for all analysed traits in different varieties, both positive and negative influences of phytoplasma ESFY were observed. The presence of ‘Ca. P. prunorum’ in infected trees was confirmed in flower parts (only in peduncle in 70.2% of cases) and fruit parts (immature fruit flesh in 42.0% and milky kernels in 26.2% of cases), however, neither in seedlings nor in pollen.

The strong effect of pollen source and pollination time on fruit set and the yield of tissue culture-derived date palm (Phoenix dactylifera L.) trees cv. Barhee

Generally, abnormal fruit set mostly in the form of setting parthenocarpic triple fruitlets is one of the most economically important disorders, which appears in trees of numerous TC (tissue culture)-derived date cultivars including cv. ‘Barhee'. To improve normal fruit set, fruit yield and fruit quality of such Barhee trees, effect of five pollen sources (three endogenous sources; ‘Beraim’, ‘Shahani’ and ‘Zahidi’ and two internationally recognized varieties; ‘Fard No. 4’ and ‘Jarvis No. 1’) at two pollination times (day of natural spathe cracking (DNC)11DNC; day of natural spathe cracking. and two days later (DNC+2)22DNC+2; two days after DNC.) was investigated on young TC-derived ‘Barhee’ trees. The study was conducted as split-plot in a randomized complete block design (RCBD), replicated three times, in hot, arid region of the southwest of Iran during the year 2013. The results indicated that the ‘Zahidi’ pollen had caused the highest percentage of normal fruit set (avg. 50.1%) and bunch yield (3.55kg) significantly (P≤0.05) superior than the other pollen sources, followed by Jarvis No. 1 (36.6%). The pollination with ‘Beraim’ pollen produced the lowest percentage of normal fruits (21.3%). The pollination at DNC was significantly (P≤0.05) higher in normal fruit set and bunch yield. The pollination with ‘Zahidi’ pollen at DNC brought the highest percentage of normal fruit set (57.5%) and maximum bunch yield (4.59kg) with acceptable fruit weight and size. Both mentioned factors and the interactive effect significantly (P≤0.05) influenced bunch ripeness. The pollen of ‘Jarvis No. 1’ at DNC yielded the highest percentage of bunch ripeness (96.91%). This pollen which had the second best normal fruit set and bunch yield was superior in showing off key metaxeic effects i.e. fruit volume, fruit weight, and pulp to seed ratio (w/w). The pollination at DNC significantly (P≤0.05) led to higher fruit length, diameter, volume and weight. Ultimately, we concluded ‘Zahidi’ pollen as the best choice for increasing normal fruit set and economical yield, ‘Jarvis No. 1’ pollen as the most suitable pollen source to benefit metaxenic effects and DNC as the best time for pollination of the TC-derived Barhee trees exhibiting abnormal fruit set and poor yield.

Northern Highbush Blueberry Cultivars Differed in Yield and Fruit Quality in Two Organic Production Systems from Planting to Maturity

Northern highbush blueberry (Vaccinium corymbosum L.) cultivars were evaluated from planting (Oct. 2006) through 2014 in a certified organic research site in Aurora, OR. The treatments included cultivar (Duke, Bluecrop, Reka, Bluejay, Bluegold, Draper, Legacy, Liberty, Ozarkblue, and Aurora), amendment-mulch [“compost + sawdust” (included preplant amendment and a surface mulch of either an agricultural on-farm crop waste compost or yard-debris compost and sawdust), and “weed mat” (no preplant amendments but with a sawdust mulch topped with weed mat)]. Adding on-farm compost as a preplant amendment and as part of the mulching program increased soil pH from 4.9 to 6.9, organic matter content (OM), and calcium (Ca), magnesium (Mg), and potassium (K) levels compared with the weed mat treatment. The reduced plant growth and yield in some cultivars grown in the compost + sawdust treatment was likely due to the higher soil pH. ‘Bluegold’ and ‘Draper’ were among the cultivars with consistently high flower bud set (40% to 57%), whereas others had consistently low values (e.g., 22% to 45% in ‘Bluecrop’). The number of flowers per bud was affected only by cultivar. There was no effect of year or amendment-mulch treatment on percent fruit set which averaged 93% during the study; however, ‘Ozarkblue’ had a significantly lower fruit set (88%) than only ‘Aurora’ (96%). Berry weight was affected by year (plant age), cultivar, and amendment-mulch treatment. ‘Ozarkblue’ produced the largest berries. Type of amendment-mulch had little effect on berry weight, except in ‘Ozarkblue’, ‘Aurora’, and ‘Reka’ where plants grown with weed mat produced larger fruit than those grown with compost + sawdust. On average, ‘Bluejay’, ‘Draper’, and ‘Liberty’ fruit had the highest percent soluble solids (TSS) and ‘Ozarkblue’ the lowest. Fruit harvested from plants grown with weed mat were firmer than when compost + sawdust was used. ‘Draper’ fruit were much firmer than those of the other cultivars in all years of the study. The number of flower buds per plant multiplied by the number of flowers/bud and berry weight (cultivar specific) and average fruit set was a good predictor of yield in young plants. Yield per plant increased from the second through seventh growing seasons as plants matured in all cultivars except for ‘Duke’ which had the greatest yield in 2014. Cumulative yield was highest in ‘Legacy’ and lowest in ‘Bluejay’ and in ‘Draper’, which had relatively low yield when plants were young. Most cultivars had greater yield when grown with weed mat, whereas ‘Bluegold’ and ‘Liberty’ were unaffected by amendment-mulch treatment. Because weeds were managed in all plots, the cultivar response to amendment-mulch was likely a reflection of sensitivity to preplant amendment with on-farm compost and the resulting higher soil pH. It is possible that the cultivars differed in their adaptability to the various fertility regimes caused by the amendment-mulch treatments and fertilizers used in our study.

Agronomic, cytogenetic and molecular studies on hermaphroditism and self-compatibility in the Greek kiwifruit (Actinidia deliciosa) cultivar ‘Tsechelidis’

abstractThe development of hermaphrodite cultivars of kiwifruit (Actinidia deliciosa) to overcome dioecism is a priority for all breeding programmes, worldwide. If successful, the number of pollinators in the orchard could be reduced, allowing more space for reproductive vines. Hermaphroditism and the expression of self-compatibility were studied in A. deliciosa, using the new kiwifruit cultivar, ‘Tsechelidis’, as a model. This plant material was chosen for investigation as its female flowers produced viable pollen. The aim of the present study was to investigate the expression and nature of self-compatibility in ‘Tsechelidis’ and to evaluate its potential for breeding purposes. The expression of self-compatibility in ‘Tsechelidis’, between years, was investigated by controlled self-pollination of female flowers in the field and by microscopic studies on pollen viability in the laboratory. The commercial cultivar ‘Hayward’ and the pollinator ‘Matua’ were used as controls. Controlled self-pollination in the field confirmed that ‘Tsechelidis’ exhibited a degree of hermaphroditism and self-compatibility. Its flowers produced viable pollen and could set fruit of an acceptable size and quality after self-pollination, compared to open-pollinated fruit. The average fruit set percentage for ‘Tsechelidis’ was 34%, and ranked from 20% to 60% per vine, while the corresponding rate for ‘Hayward’ was only 4%. Microscopic studies on ‘Tsechelidis’ pollen revealed variations in pollen viability between different vines, which were even greater between different flowers on the same vine, ranging, in some cases, from 0% (absolutely sterile) to 70% (significantly fertile) per flower. Female control ‘Hayward’ vines were found to be practically sterile (0%), while male control ‘Matua’ vines were almost 100% fertile. The nature of self-compatibility in ‘Tsechelidis’ was investigated further by molecular analysis using the sex-linked sequence characterised amplified region (SCAR) markers, SmX, SmY, and SmY1, and by single nucleotide polymorphism (SNP) analysis. Hermaphroditism in ‘Tsechelidis’ was related to sex expression, as observed by SNP analysis, but complete genome mapping would be required to fully understand the mechanisms involved and to exploit this new genetic material for breeding purposes.

METHOD FOR OVERCOMING THE PASSION FRUIT SELF-INCOMPATIBILITY

ABSTRACT The methodology of self-pollination of passion fruit flowers at anthesis after stigma excision was proposed. This method was compared with self-pollination procedures at anthesis and at the stage of flower bud. Two genotypes (M7 and N9), propagated by cuttings were studied. Self-pollinations were performed at 1 pm, 1 pm and 5 pm or 5 pm. Fruit set (%), fruit mass (g), pulp mass (g), pulp/fruit ratio and seed number per fruit were evaluated and compared to fruits derived from M7 x N9 and N9 x M7 crosses. No fruit set was obtained from self-pollination at anthesis, which confirms the self-incompatibility of both genotypes. Self-pollination after stigma excision was the best procedure, reaching average fruit set of 73.61 % (13 hours) and 81.94 % (double self-pollination at 1 pm and 5 pm). Although two self-pollinations after stigma excision at anthesis is more efficient, performing only one self-pollination at 1 pm requires less labor. The amount of seeds produced per fruit is satisfactory to generate inbred population.

NEBC 120th Anniversary Botanical Research Conference Presentations

The consequences of initial variability in reproductive effort on later pollination and fruit development have frequently been investigated with flower removal experiments. Often, plants produce many fewer fruits than flowers, so flower removal might not be expected to alter subsequent growth or development patterns all that much. Yet, many studies have demonstrated such changes even for species with low average fruit set, which begs for an explanation. Many (at least seven, by our count) such explanations have been reported in the literature, but experimental support for most is limited. In summer 2014, we conducted a field experiment on a lowbush blueberry (Vaccinium angustifolium) farm in Maine. In this experiment, we coupled flower removal with three other treatments, each designed to assess the validity of one of three often-cited hypotheses invoked to explain why growth and development changes occur following flower removal: 1) “Short-term nutrient shortages;” 2) “spatiotemporal limitations;” and 3) “the compound interest effect.” The three respective treatments—foliar nitrogen fertilization, positionally biased flower removal, and defoliation—were designed to either intensify or weaken the apparent effects of flower removal if the corresponding hypothesis had merit. As in a 2013 preliminary experiment, flower removal elicited several statistically significant growth and development changes in blueberry, including increases in final leaf area, ripe fruit weight, fruit ripening rate, and relative fruit production. The additional treatments also elicited several significant plant responses, though not always with concomitant flower removal effects as well. For example, fertilization generally increased fruit cluster mass by harvest, but flower removal itself had no such effect on cluster mass. Most observed interactive effects between flower removal and the additional treatments either ran counter to expectations, were limited in scope, or couldn't be unambiguously interpreted. For at least a few observed changes, none of the additional treatments significantly altered the effects of flower removal. We conclude that current hypotheses for the mechanistic basis for changes induced by flower removal are inadequate, at least for blueberry, a species with frequently low fruit set even when managed commercially. However, strong intellectual and economic imperatives exist to encourage further investigation into this open question.Plants grown in horticulture or occurring as adventives outside their native range can provide insight into species’ fundamental niche requirements that might not be evident from the native range, or realized niche, alone. Such occurrences can also identify conditions that support individual survival, but do not currently sustain positive population growth (i.e., a species’ ‘tolerance niche’). Further, in the context of rapid climate change, horticultural and adventive occurrences beyond current range edges might circumvent natural dispersal limitations and facilitate species range shifts. To explore these concepts in the field, we investigated the history and structure of five newly discovered populations of naturalized Magnolia tripetala near horticultural sites in western Massachusetts, USA. This tree species is native to the southeastern US, but has been grown horticulturally in the Northeast since the 1800s. However, naturalized populations had not been well documented in the region previously, raising the possibility that the species’ escape has been triggered by recent climate change. With tree coring and life stage surveys, we asked whether the naturalized populations exhibited synchronous patterns of establishment and expansion, suggestive of climatic release and a shift from tolerance niche to fundamental niche conditions in the region. Across the five sites, we documented 660 individuals, with populations ranging in size from 46 to 396 individuals, including seedlings, saplings, and reproduct